I've got the Intel DG45ID, latest BIOS, G45 chipset and video drivers (Windows 7 32-bit), so I think those bases are covered.
kipster - thanks for the tip, I will do some research on the registry edits you mention. Sounds like your setup is almost identical to mine, so at least I know the combo *should* be workable which make me feel a little more optimistic. The only thing though is I don't even see the boot screen, so the problem seems to be pre-Windows, which means drivers/registry haven't come into play at that point. But I'll still look into it.
cybrsage - I'll try HDMI 4. I have tried both 1 and 2, but not 4. I did notice that each HDMI port has a little different default settings based on the device label. I'll take a closer look at those and see if I can note a difference.
Really though, there aren't that many settings available. Basically I have upconvert/upcale OFF, though I tried several combinations of resolution upscaling as well. I've tried input mode set to Auto as well as HDMI. I'm not really sure there's anything else to change.
nobisita - I read some other posts about issues with when the device is turned on, so I tried that as well. Shut down PC AND receiver. Turned the receiver on to the HTPC input, then turned on the PC, no dice. Then tried it vice-versa. Interesting thing is, through the DVI-to-HDMI adapter, it doesn't seem to care what's on when, I get a picture immediately regardless of what order I turn on or switch inputs, and I can go back and forth between inputs just fine.
I am curious as to what the difference is in the signal between direct HDMI as opposed to DVI-to-HDMI. Why no picture direct, but picture pops right up with the DVI-to-HDMI adapter? Seems like the answer to that has to point to the cause of the issue.